Quantitative Precipitation Forecast
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FOUS30 KWBC 210830
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
430 AM EDT SUN AUG 21 2016

...VALID 12Z SUN AUG 21 2016 - 12Z MON AUG 22 2016...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
25 SSE CWYQ 10 WNW PQI 25 NE MLT 15 NE BGR 15 SSW MVY
55 ESE MJX 60 E OXB 50 SE OXB 50 SE MFV 15 NNE NTU 10 NE JGG
15 NW FYJ 10 WSW OMH 15 SW SHD 15 NE ROA 10 SSW GEV 20 SSE 1A5
20 NNE 47A 20 E CHA 15 SSE CSV 30 SSE SME 40 W I16 30 WNW 48I
25 NW CKB PIT 15 NNE FKL 20 ENE BUF 35 SSE CWRK CYWA.

MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
55 SE YUM 15 SE BLH 20 NE BLH 50 SE EED 45 SE IGM 35 E IGM
60 N IGM 20 SSW SGU 55 W PGA 50 SSE PGA 50 NE INW 25 SSW GUP
35 N GNT 15 E FMN 30 NNE DRO 35 S GUC 35 SSE MYP VTP 15 SSW RTN
55 E CQC 20 ENE ROW 20 ESE CNM 20 E PEQ 55 SSE MAF 25 NNW 6R9
15 N LHB 35 ESE OCH 20 N IER 30 SSW MLU 25 NE HEZ 25 NNE MCB
25 SE MCB 20 SSW HDC 25 N 7R3 15 WNW PTN 15 NE KCMB KXIH
20 S PSX 2R8 25 NE EBG 55 WSW MMRX.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
80 ESE DUG 25 S SVC 25 NNE SVC 30 SW AEG 30 NNE AEG 10 SSW SAF
10 SSW CQC 4CR 30 SE SRR 45 SW ATS 20 WSW GDP 40 SSW GDP
85 SE MMCS.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
30 S CWQO 45 W PQI 40 NW MLT 20 N GNR 30 WSW GNR 40 ENE BML
10 ESE BML 10 ENE MWN 20 NNW 1P1 LEB 10 S VSF 10 E AQW 15 SW RUT
10 N BTV 20 SW CWFQ 10 SSE CMLI.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
85 SSW 6R6 55 SSE 6R6 20 N DRT 20 ESE ECU 25 N SAT 30 ESE 3T5
5R5 10 W PSX 10 SSE BKS 40 WNW MFE 40 ENE MMMY.

MODERATE RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
40 WSW MMPG 20 SSE DLF 25 NW UVA SAT 30 ESE BAZ 20 NNW VCT
15 WSW VCT 35 SW VCT 10 N BKS BKS 30 S HBV 55 SSW HBV
45 NNE MMAN.

HIGH RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
25 NW HBV 10 N LRD 30 NNW LRD 40 WSW COT 35 W COT 35 S UVA
25 S HDO 25 SSE HDO 15 SW SSF 20 SSE SSF 30 SSE SSF 50 NNW ALI
25 W ALI 10 N HBV 25 NW HBV.



SOUTH CENTRAL TO SOUTH TEXAS

VERY HEAVY TO EXCESSIVE RAINFALL POTENTIAL WILL CONTINUE INTO THE
NEW DAY 1 TIME PERIOD ACROSS SOUTH CENTRAL TO SOUTH TX FROM IN THE
VICINITY OF 100W NEAR THE U.S./MEXICAN BORDER--NORTHEASTWARD NEAR
OR JUST TO THE EAST OF SAN ANTONIO.  THE PREVIOUS MODERATE AND
HIGH RISK AREAS WERE SHIFTED SOUTHWARD CENTERED ON THE SOUTHERN
PORTION OF THE EWX...MOST OF CRP AND THE NORTHWEST PORTION OF BRO
WFOS.  MODEL VERIFICATION SO FAR POINTS TO A NORTHWARD BIAS IN THE
MODEL QPFS.  WHILE MANY OF THE MODELS AREA SHOWING THIS
BIAS---THEY ALSO SHOW LITTLE MOVEMENT TO THEIR PRIMARY AREA OF
POTENTIALLY VERY HEAVY RAINFALL AMOUNTS DURING THE UPCOMING DAY 1
PERIOD.  THE DAY 1 QPF WENT WITH THE IDEA OF A FARTHER SOUTH
ADJUSTMENT TO THE MODELS---SHOWING LITTLE MOVEMENT THROUGH THE DAY
ON SUNDAY.  AFTER THAT---WHILE CONFIDENCE DECREASES WITH THE
EVOLUTION---THERE ARE SIGNS THAT A MCV FROM THIS CONVECTION MAY
BEGIN TO PRESS MORE TO THE WEST NORTHWEST TO THE WEST OF 10OW
ALONG THE BORDER REGION.   WPC QPF FAVORED THE MODEL CONSENSUS OF
KEEPING THE GREATEST AMOUNTS TO THE SOUTH OF 30N...NOT FAVORING
ANY SIGNIFICANT NORTHEASTWARD PUSH OF HEAVY PRECIP AS PER THE
PREVIOUS EC RUNS. THE DAY 1 QPF IS MORE IN LINE WITH THE GFS---GFS
REFORECAST---UKMET---HI RES ARW---NSSL WRF AND NAM CONEST.  WHILE
THE PLACEMENT OF THE MAXIMA IN THE MODELS HAS NOT BEEN
PERFECT---THEY HAVE SIGNALED OVER THE PAST FEW RUNS FOR VERY HEAVY
AMOUNTS---WITH THIS SAME SIGNAL CONTINUING IN THE UPCOMING DAY 1
TIME PERIOD.  WITH THE SLOW MOVEMENT TO THE IS CONVECTIVE AREA
EXPECTED TO CONTINUE INTO THE NEW DAY 1 PERIOD---SERIOUS FLOODING
PROBLEMS MAY PERSIST ACROSS THESE AREAS---WITH ADDITIONAL
LOCALIZED MAX AMOUNTS OF 5-10"+ POSSIBLE.

CENTRAL APPALACHIANS---MID ATLANTIC INTO THE NORTHEAST/NEW ENGLAND

NO MAJOR MODEL DISAGREEMENTS WITH THE EASTWARD PUSH OF THE
AMPLIFIED UPPER MS VALLEY TROF.  THIS SYSTEM EXPECTED TO PUSH
STEADILY EAST NORTHEASTWARD THROUGH THE LAKES/OH VALLEY---MID
ATLANTIC AND NORTHEAST.  A NARROW AXIS OF ABOVE AVERAGE PW
VALUES---2 TO 2.5 STANDARD DEVIATIONS ABOVE THE MEAN---WILL
PERSIST ALONG AND AHEAD OF THE ASSOCIATED FRONT.  STRONG FRONTAL
CONVERGENCE IN THIS HIGH PW AXIS WILL SUPPORT POTENTIAL FOR
ORGANIZED FRONTAL/PRE-FRONTAL CONVECTION---WITH MODERATE TO HEAVY
PRECIP TOTALS FROM THE CENTRAL APPALACHIANS---THROUGH THE MID
ATLANTIC AND INTO THE NORTHEAST/NEW ENGLAND.  THE QUICK MOVEMENT
OF THE FRONT AND ASSOCIATED CONVECTION SHOULD BE A LIMITING FACTOR
FOR VERY HEAVY TOTALS---WITH ONLY A MARGINAL RISK OF RUNOFF ISSUES
OVER MOST OF THE AREA.  THE EXCEPTION WAS OVER PORTIONS OF
NORTHERN NEW ENGLAND FROM VT--NORTHERN NH AND NORTHWEST MAINE
WHERE FFG VALUES ARE RELATIVELY LOWER---WITH A GREATER RISK THAT
SHORT TERM PRECIP TOTALS OF 1"+ MAY RESULT IN RUNOFF ISSUES.  HERE
A SLIGHT RISK AREA WAS MAINTAINED FROM THE PREVIOUS DAY 2 OUTLOOK.

DESERT SOUTHWEST INTO THE SOUTHERN HIGH PLAINS

A STREAM OF SHORTWAVE ENERGY STRETCHING FROM SOUTHERN CALIFORNIA
INTO THE SOUTHWEST AND SOUTHERN HIGH PLAINS WILL SUPPORT ANOTHER
ROUND OF WIDESPREAD SCATTERED CONVECTION ACROSS THESE AREAS THIS
FORECAST PERIOD.  MODEL CONSENSUS FOR MAX TOTALS IS FROM SOUTHWEST
TX INTO CENTRAL TO WESTERN NEW MEXICO IN THE VICINITY OF THE
STATIONARY FRONTAL BOUNDARY FORECAST TO REMAIN DRAPED FROM WESTERN
NM INTO SOUTHWEST TX.  AREAL AVERAGE MODERATE TOTALS
DEPICTED---WITH LIKELIHOOD OF HEAVIER TOTALS AND ISOLATED RUNOFF
ISSUES IN THE VICINITY OF THIS FRONT.  A SLIGHT RISK AREA WAS
ADDED OVER PORTIONS OF FAR SOUTHWEST TX INTO CENTRAL NM.  ISOLATED
RUNOFF ISSUES ALSO POSSIBLE WESTWARD INTO CENTRAL TO SOUTHERN
ARIZONA WITH THE NEXT ROUND OF SCATTERED CONVECTION ACROSS THIS
REGION LATE SUNDAY INTO THE EARLY MORNING HOURS OF MONDAY.  HERE A
MARGINAL RISK IS DENOTED.


ORAVEC
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